Memantine pamoate, method of preparation and use thereof

ABSTRACT

The composition containing a pamoate salt of donepezil, the method of preparation and the use thereof are disclosed.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This is a divisional of U.S. patent application Ser. No. 15/134,182,filed on Apr. 20, 2016, which is a divisional of U.S. patent applicationSer. No. 14/357,283, filed on May 9, 2014, now U.S. Pat. No. 9,353,059,which is a U.S. national stage entry of International Patent ApplicationNo. PCT/CN2012/085534, filed on Nov. 29, 2012, which is acontinuation-in-part of International Patent Application No.PCT/CN2011/083117, filed on Nov. 29, 2011, the entire contents of eachof which are fully incorporated herein by reference.

TECHNICAL FIELD

The invention relates to pamoate salts, and more particularly, topamoate salts of donepezil, rivastigmine and memantine, pharmaceuticalcompositions comprising such salts, methods of preparing such salts, andmethods of treating a subject in need thereof with such salts andcompositions.

BACKGROUND

Polymeric extended release systems for the treatment of dementia of theAlzheimer's type have been described. However, such extended releasedevices tend to be costly to manufacture and difficult to produce. Inaddition, they typically provide for once-daily oral administration.Thus, there still exists a need for improved methods of delivering suchagents which maximize the medical benefits of the active agent, can beadministered more conveniently at a dosing interval longer than 24hours, and can be produced in a more cost effective manner.

The chemical structure of donepezil is:

The molecular weight of donepezil is 379.49, the melting point is 207°C., and the pK_(a) is 9.1.

Donepezil has been successfully used in the treatment of dementia (abrain disorder that affects the ability to remember, think clearly,communicate, and perform daily activities and may cause changes in moodand personality) associated with Alzheimer's disease and is currentlybeing marketed for that purpose. Such dementia patients are oftennon-compliant, making it difficult to assess whether or not a patienthas received the proper dosage of medication. Applicants have discoveredthat it can be especially desired to formulate donepezil in a depotformulation or as an intramuscular formulation to assure consistent andproper dosage of the drug substance and to maximize the clinicalbenefits through improved patient compliance.

Donepezil is an organic weak base. In solution, it exists as the freebase form at high pH (alkaline conditions). Aqueous solubility ofdonepezil increases with decreasing pH of the solution due to anincreasing fraction of the drug being ionized. At high concentrations ofthe ionized drug (protonated amine), the solubility product of the salt(K_(sp)) will be exceeded and the salt form will precipitate out. Thenature of the drug and counterion determine the K_(sp) and theassociated solid state properties of the salt.

There are a wide range of counterions that have been used to preparesalts of bases using inorganic and organic acids. The most frequentlyused anion to form a salt of a basic drug is the hydrochloride form. Forexample, Aricept®, a commercial product of donepezil for oraladministration, uses hydrochloride salt. Multiple organic salts ofdonepezil are also described in U.S. Patent Application Pub. No.2008/0194628 by Mezei et al. These salts were prepared to improvestability, solubility or increased dissolution rate for oraladministration. They possess desirable properties for immediate releasedosage form. However, when extended release delivery of these salts aredesired for a prolonged action, extended release technology usingrate-controlling polymers are usually required as described in U.S.Patent Application Pub. No. 2011/0218216 by Vivek et al. and by P. Zhanget al, in Biomaterials (2007, 28(10):1882-8). In addition, such extendedrelease devices tend to be costly to manufacture and difficult toproduce at commercial scale. Thus, there still exists a need forimproved methods of delivering such agents which maximize the medicalbenefits of the active agent, can be administered significantly lessfrequently than the current 24-hour dosing interval and can be producedin a more cost effective manner.

The chemical structure of pamoic acid is:

The molecular weight of pamoic acid is 388 g/mol, the pK_(a1) is 2.51,and pK_(a2) is 3.1.

It is known that the pH of muscle tissue can vary with exercise, stress,and injury which can affect drug solubility, and thus the rate ofabsorption of injectable drugs. Therefore, it is desirable to find aninjectable extended release formulation in which the release rate of theactive ingredient is minimally dependent on pH.

SUMMARY

The present invention is directed to a variety of solid state forms,namely, pamoate salts, and more particularly, to pamoate salts ofdonepezil, pamoate salts of rivastigmine and pamoate salts of memantine.In addition, the present invention also relates to pharmaceuticalcompositions comprising such salts, methods of preparing such salts, andmethods of treating a subject or patient (such as a human) in needthereof with such salts and pharmaceutical compositions. The presentinvention also relates to the discovery that pamoate salts of donepezilprovide a desirable long acting and/or extended release profile.

In an aspect, the disclosure provides novel pamoate salts of donepezil.In some aspects, the ratio of donepezil free base to pamoic acid is 1:1(which is referred to herein as the mono-pamoate salt of donepezil). Insome embodiments, the ratio of donepezil free base (2) to pamoic acid(1) is 2:1 (which is referred to herein as the semi-pamoate salt ofdonepezil). In some aspects, the salt is (1) crystalline, includinganhydrous, hydrate, solvate forms and their polymorphs, or (2)amorphous. The above described salts are especially useful in preparingan extended release formulation (or composition) in which the releaserate is minimally dependent on the pH of the environment.

In another aspect, the present invention provides a pharmaceuticalcomposition comprising donepezil pamoate and at least onepharmaceutically acceptable carrier. In some aspects, the carrier is aviscous aqueous or nonaqueous carrier.

In further aspect, the present invention provides a method of preparinga pamoate salt of donepezil comprising treating or mixing of donepezilwith pamoic acid or treating or mixing a donepezil salt with a pamoatesalt in solvent.

In another aspect, the present invention provides a method of treating asubject having dementia associated with Alzheimer's disease comprisingthe step of administering a therapeutically effective amount of apharmaceutical composition comprising a pamoate salt of donepezil and atleast one pharmaceutically acceptable carrier to a subject in need oftreatment thereof. In some aspects, the composition is administered byinjection. In some aspects, the composition is administeredintramuscularly or subcutaneously.

It has been discovered that a formulation (or composition) comprising apamoate salt of donepezil as an active ingredient or active agent, andone or more pharmaceutically acceptable carriers, can address the longfelt need for a stable, pharmaceutically elegant formulation with acontrollable release rate which may be useful as a depot formulation orfor intramuscular or subcutaneous use.

In another aspect, the present invention relates to pamoate salts ofrivastigmine. In some embodiments, the salt is (1) crystalline,including anhydrous, hydrate, solvate forms and their polymorphs, or (2)amorphous. In yet another aspect, the present invention relates topharmaceutical compositions containing pamoate salts of rivastigmine andat least one pharmaceutically acceptable carrier. In still yet anotheraspect, the present invention provides a method of treating a subjecthaving dementia associated with Alzheimer's disease comprisingadministering a therapeutically effective amount of a pharmaceuticalcomposition comprising a pamoate salt of rivastigmine and at least onepharmaceutically acceptable carrier to a subject in need thereof. Insome aspects, the composition is administered by injection. In someembodiments, the composition is administered intramuscularly orsubcutaneously.

In still yet another aspect, the present invention relates to pamoatesalts of memantine. In some embodiments, the salt is (1) crystalline,including anhydrous, hydrate, solvate forms and their polymorphs, or (2)amorphous. In yet another aspect, the present invention relates topharmaceutical compositions containing pamoate salts of memantine and apharmaceutically acceptable carrier. In still another aspect, In anotheraspect, the present invention provides a method of treating a subjecthaving dementia associated with Alzheimer's disease comprisingadministering a therapeutically effective amount of a pharmaceuticalcomposition comprising a pamoate salt of memantine and at least onepharmaceutically acceptable carrier to a patient in need thereof. Insome aspects, the composition is administered by injection. In someembodiments, the composition is administered intramuscularly orsubcutaneously.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict two salt forms of donepezil pamoate, a 1:1 and2:1 ratio of donepezil to pamoic acid, respectively.

FIG. 2 depicts the x-ray powder diffraction (“XRPD”) spectrum ofdonepezil pamoate (1:1 ratio of donepezil to pamoic acid) obtained fromdonepezil and pamoic acid in DMSO/water.

FIG. 3 depicts the XRPD spectrum of donepezil pamoate (2:1 ratio ofdonepezil to pamoic acid) obtained from donepezil and pamoic acid inDMSO/water.

FIG. 4 depicts the XRPD spectrum of donepezil pamoate (2:1 ratio ofdonepezil to pamoic acid) obtained from donepezil hydrochloride anddisodium pamoate in water.

FIG. 5 depicts the XRPD spectrum of donepezil pamoate (1:1 ratio ofdonepezil to pamoic acid) obtained from donepezil hydrochloride anddisodium pamoate in ethanol.

FIG. 6 depicts the differential scanning calorimetry thermograms ofdonepezil pamoate (1:1 and 2:1).

FIG. 7 depicts the thermogravimetric analysis thermograms of donepezilpamoate (1:1 and 2:1).

FIG. 8 depicts the NMR spectrum of donepezil pamoate (1:1 ratio ofdonepezil to pamoic acid) prepared in DMSO/water.

FIG. 9 depicts the NMR spectrum of donepezil pamoate (2:1 ratio ofdonepezil to pamoic acid) prepared in DMSO/water.

FIG. 10 depicts the NMR spectrum of donepezil pamoate (1:1 ratio ofdonepezil to pamoic acid) prepared in ethanol.

FIG. 11 depicts the mean plasma concentration of donepezil after asingle dose (13.5 mg/kg) of an intramuscular injection of donepezilpamoate (2:1) suspension (n=5) and donepezil hydrochloride solution(n=5) in female rats respectively as shown in Example 7.

FIG. 12 depicts the X-ray powder diffraction spectrum of donepezilpamoate hydrated form as described in Example 9.

FIG. 13 depicts the X-ray powder diffraction spectrum of donepezilpamoate anhydrous form as described in Example 9.

FIG. 14 depicts an X-ray powder diffraction spectrum of rivastigminepamoate salt as described in Example 10.

FIG. 15 depicts the differential calorimetry diagram for rivastigiminepamoate salt as described in Example 10.

FIG. 16 depicts the NMR spectra of rivastigmine pamoate salt asdescribed in Example 10.

FIG. 17 depicts an X-ray powder diffraction spectrum of memantinepamoate salt as described in Example 11.

FIG. 18 depicts the differential calorimetry diagram for memantinepamoate salt as described in Example 11.

FIG. 19 depicts the NMR spectra of memantine pamoate salt as describedin Example 11.

DETAILED DESCRIPTION

The present invention relates to solid state or solid forms of donepezilsalts, wherein the salt is a pamoate salt. Among other advantages,pamoate salts of donepezil provide a desired long acting and/or extendedrelease profile. Such pamoate salts of donepezil can be used to treatpatients suffering from dementia, including, patients suffering fromAlzheimer's disease.

Before a detailed explanation of the various aspects of the invention,it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement ofcomponents set forth in the following description. The invention iscapable of other embodiments and of being practiced or of being carriedout in various ways.

It also is specifically understood that any numerical value recitedherein includes all values from the lower value to the upper value,i.e., all possible combinations of numerical values between the lowestvalue and the highest value enumerated are to be considered to beexpressly stated in this application.

In one aspect, the invention includes pamoate salts of donepezil andcompositions and formulations containing said pamoate salts. Preferably,the pamoate salt is characterized by a ratio of donepezil to pamoic acidof 1:1 or 2:1. The pamoate salt can be crystalline, anhydrous, hydrated,solvated, or amorphous.

In another aspect, the invention relates to crystalline pamoate salts ofdonepezil having or characterized by one or more of the followingproperties: (1) a powder X-ray diffraction pattern having main peaksexpressed as 2-theta at about 21.1, 22.4, and 24.5±0.2 degrees 2-theta;(2) an X-ray power diffraction pattern substantially in accordance withthat shown in FIG. 2; (3) a molar ratio of donepezil to pamoic acid of1:1; and (4) combinations of (1), (2) or (3). Additionally, thecrystalline pamoate salts of donepezil can further have or becharacterized by the powder X-ray diffraction pattern shown in Table 1.

In yet another aspect, the invention relates to crystalline pamoatesalts of donepezil having or characterized by one or more of thefollowing properties: (1) a powder X-ray diffraction pattern having mainpeaks expressed as 2-theta at about 12.2, 19.2, 22.3 and 23.3±0.2degrees 2-theta; (2) an X-ray power diffraction pattern substantially inaccordance with that shown Figure; (3) a molar ratio of donepezil topamoic acid of 2:1; and (4) combinations of (1), (2) or (3).Additionally, the crystalline pamoate salts of donepezil can furtherhave or be characterized by the powder X-ray diffraction pattern shownin Table 2.

In yet another aspect, the invention relates to crystalline pamoatesalts of donepezil having or characterized by one or more of thefollowing properties: (1) a powder X-ray diffraction pattern having mainpeaks expressed as 2-theta at about 9.4, 14.8, and 17.8, 22.0 and22.3±0.2 degrees 2-theta; (2) a molar ratio of donepezil to pamoic acidof 1:1; and (3) combinations of (1) or (2). Additionally, thecrystalline pamoate salts of donepezil can further have or becharacterized by the powder X-ray diffraction pattern shown in Table 3.

In yet another aspect, the present invention relates to a form of apamoate salt of donepezil selected from the group consisting of: (1)pamoate salt of donepezil Form A (also known as the “Hydrated Form”)having or characterized by a powder X-ray diffraction pattern havingmain peaks expressed as 2-theta at about 11.6, 12.3, 18.8, 19.3, 23.3,24.6 and 27.3±0.2 degrees 2-theta; and (2) pamoate salt of donepezilForm B (also known as the “Anhydrous Form”) having or having orcharacterized by a powder X-ray diffraction pattern having main peaksexpressed as 2-theta at about 6.3, 11.9, 14.0, 16.2, 20.4, 21.1 and23.7±0.2 degrees 2-theta.

In another aspect, the present invention relates to a pamoate salt ofdonepzil Form A having or characterized by a powder X-ray diffractionpattern having main peaks expressed as 2-theta at about 11.6, 12.3,18.8, 19.3, 23.3, 24.6 and 27.3±0.2 degrees 2-theta and furthercharacterized by an x-ray diffraction pattern substantially inaccordance with that shown in FIG. 12. Moreover, a pamoate salt ofdonepzil Form A (also known as the “Hydrated Form”) can further have orbe characterized by the powder X-ray diffraction pattern shown in Table5.

In another aspect, the present invention relates to a pamoate salt ofdonepzil Form B (also known as the “Anhydrous Form”) having orcharacterized by a powder X-ray diffraction pattern having main peaksexpressed as 2-theta at about 6.3, 11.9, 14.0, 16.2, 20.4, 21.1 and23.7±0.2 degrees 2-theta and further characterized by an x-raydiffraction pattern substantially in accordance with that shown in FIG.13. Moreover, a pamoate salt of donepzil Form A can further have or becharacterized by the powder X-ray diffraction pattern shown in Table 6.

The invention further relates to a pharmaceutical composition comprisingpamoate salts of donepezil and at least one pharmaceutically acceptablecarrier. In one preferred embodiment, the pharmaceutical composition isan extended release formulation comprising pamoate salts of donepeziland a polymer. In another embodiment, the pharmaceutically acceptablecarrier is a viscous aqueous or nonaqueous fluid. In a preferredembodiment, the pharmaceutical composition releases an effective amountof the active agent (pamoate salt of donepezil) over a period of atleast about 24 hours or at least about 48 hours. In another preferredembodiment, the active agent in the pharmaceutical composition has aduration of efficacy of at least about 7 days or at least about 14 days.

The invention further relates to methods of treating a subject, such asa warm blood mammal (such as a human patient or subject), in need oftreatment thereof. The method comprises the step of administering atherapeutically effective amount of a pharmaceutical compositioncomprising a pamoate salt of donepezil and at least one pharmaceuticallyacceptable carrier.

With respect to the chemical structure of pamoic acid, both carboxyliccounter ions can form salt with the tertiary amine of donepezil,resulting in a ratio of donepezil to pamoic acid of 1:1 or 2:1, such asdescribed in the FIG. 1.

It has been discovered that the pharmaceutically acceptable salts ofdonepezil formed using pamoic acid as a counterion surprisingly exhibitvery low solubility (K_(sp)). This low solubility is highly desirablewhen used in a pharmaceutical composition to provide for extendedrelease of the pamoate salt of donepezil when administeredintramuscularly or subcutaneously. The pharmaceutical compositions ofthe present invention include various pharmaceutical dosage forms forpurposes of administration to a subject (such as a warm blooded mammal,such as a human) in need of treatment thereof. To prepare thepharmaceutical compositions of the present invention, a pharmaceuticallyeffective amount of one or more pamoate salts of donepezil (as theactive ingredient or active agent) are combined with one or morepharmaceutically acceptable excipients. The pharmaceutically acceptableexcipients used are not critical, are well known in the art, and maytake a wide variety of forms depending on the form of preparationdesired for administration. These pharmaceutical compositions aredesirably in unitary dosage form suitable for administration.

Administration of the compositions of the present invention can beparenterally, such as by subcutaneous or intramuscular injection orimplantation. For administration, the pamoate salts of donepezil can besuspended in an aqueous solvent, which may further comprise a wettingagent, such as the polyoxyethylene derivatives of sorbitan esters, e.g.polysorbate 80 (Tween® 80) and polysorbate 20 (Tween® 20), lecithin,polyoxyethylene- and polyoxypropylene ethers, sodium deoxycholate, andthe like; a suspending agent such as a cellulose derivate, e.g.methylcellulose, sodium carboxymethylcellulose and hydroxypropylmethylcellulose, polyvinylpyrrolidone, alginates, chitosan, dextran,gelatin, polyethylene glycols, polyoxyethylene- and polyoxypropyleneethers and the like; an acid, e.g. hydrochloric acid, and the like; abase, e.g. sodium hydroxide, and the like; a buffer comprising a mixtureof appropriate amounts of an acid such as phosphoric, succinic,tartaric, lactic, acetic, maleic or citric acid, and a base, inparticular sodium hydroxide or disodium hydrogen phosphate; apreservative, e.g. benzoic acid, benzyl alcohol, butylatedhydroxyanisole, butylated hydroxytoluene, chlorbutol, a gallate, ahydroxybenzoate, EDTA, phenol, chlorocresol, metacresol, benzothoniumchloride, myristyl-γ-piccolinium chloride, phenylmercuri acetate,thimerosal and the like; a tonicity adjusting agent, e.g. sodiumchloride, dextrose, mannitol, sorbitol, lactose, sodium sulfate, and thelike. Alternatively, the pamoate salts of donepezil may be formulated inone or more oils. Appropriate oils that can be used include fixed oils,for example, peanut oil, sesame oil, cottonseed oil, corn oil, saffloweroil, castor oil, ethyloleate, soybean oil, synthetic glycerol esters oflong chain fatty or medium chain acids and mixtures of these and otheroils. Also, thickening agents may be added to the composition, e.g.aluminum monostearate, ethylcellulose, triglycerides, hydrogenatedcastor oil, and the like.

In view of the usefulness of the pamoate salts of donepezil in thetreatment of dementia of Alzheimer type diseases, it is evident that thepresent invention further provides a method of treating warm-bloodedmammals (such as humans), suffering from Alzheimer's diseases. Such amethod comprises the step of administering a therapeutically effectiveamount of a pharmaceutical acceptable composition comprising at leastone pamoate salt of donepezil (also more generally referred to as the“active agent” herein) as described herein with one or morepharmaceutically acceptable excipients.

The pharmaceutically acceptable composition can be administered to asubject in need of treatment thereof as a long acting composition. Inone aspect, the active agent is released from the composition over aperiod of at least about 24 hours, preferably about 48 hours. The activeagent can also be administered in an extended release composition. Inone aspect, the extended release composition releases the active agentover a period of at least about 7 days, preferably at least about 14days, alternatively for at least 2, 3, 4, 6 or 8 weeks. The compositioncan be administered by injection, such as intramuscularly orsubcutaneously. In one aspect, the compositions can be administered as asingle or sole dose. However, the compositions described herein areparticularly beneficial for those subjects in need of treatment thereofthat require constant or chronic therapy, such as those subjects thatreceive repeated doses over several weeks or months or more. In suchdosing regimens, the method can comprise the steps of: (1) administeringas first dose an first extended release composition containing thepamoate salts of donepezil as described herein followed by (2)administering as a second dose (and as subsequence doses if necessary),a second extended release composition. The second extended releasecomposition can be the same, substantially the same or different thanthe first extended release composition. Specifically, the secondextended release composition can include as the active agent the pamoatesalts of donepezil as described herein or an active agent that is otherthan the pamoate salts of donepezil as described herein. The secondcomposition can be administered at about 7 days, or more, such as atleast about 14 days, or at least about 17 days, after the firstadministration of the first extended release composition, where thefirst administration results in the release of active agent for a periodof 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 days, or more.

As used herein, the term “individual”, “subject” or “patient” refers toa warm blooded animal which is afflicted with a particular diseasestate. Warm blooded animals include mammals, such as humans.

The term “therapeutically effective amount” is defined as an amountresulting in the improvement of any parameters or clinical symptoms. Theactual dose may vary with each patient and does not necessarily indicatea total elimination of all disease symptoms. A therapeutically effectiveamount of the compound used in the methods described herein can bereadily determined by one skilled in the art, such as an attendingphysician, by observing results obtained under analogous circumstancesand by using conventional techniques. In determining the therapeuticallyeffective dose, the attending physician considers a number of factors,including, but not limited to: the species of mammal; its size, age, andgeneral health; the specific disease involved; the degree of involvementor the severity of the disease; the response of the individual patient;the particular compound administered; the mode of administration; thebioavailability characteristic of the preparation administered; the doseregimen selected; the use of concomitant medication; and other relevantcircumstances.

Preferred amounts and modes of administration can be readily bedetermined by one skilled in the art depending upon the particularcharacteristics of the compound selected, the disease state to betreated, the stage of the disease, and other relevant circumstancesusing formulation technology known in the art, described for example inRemington's Pharmaceutical Sciences, latest edition, Mack Publishing Co.

Pharmaceutical compositions can be manufactured utilizing routinetechniques known in the art. Typically a therapeutically effectiveamount of the compound (salt) will be combined with a pharmaceuticallyacceptable carrier.

The pharmaceutical compositions of the present invention may beadministered parenterally. For instance, they can be administered byinjection. Preferred methods of parenteral administration includeintramuscular and subcutaneous injection.

For parenteral administration, the compounds (salt) may be dissolved ina physiologically acceptable pharmaceutical carrier and administered aseither a solution or a suspension. Viscous injectable carriers arepreferred, having for example, a viscosity of at least 20 cp at 20° C.In other embodiments, the fluid phase of the suspension has a viscosityat 20° C. of at least about 30 cp, 40 cp, 50 cp, and 60 cp. Thecomposition can also comprise a viscosity enhancing agent, a densityenhancing agent, a tonicity enhancing agent, and/or a wetting agent.Suitable pharmaceutical carriers include water, saline, dextrosesolutions, fructose solutions, ethanol, or oils of animal, vegetative,or synthetic origin. The pharmaceutical carrier may also containpreservatives, and buffers as are known in the art.

When the composition is to be used as an injectable material, including,but not limited to, needle-less injection, it can be formulated into aconventional injectable carrier. Suitable carriers include biocompatibleand pharmaceutically acceptable solutions, emulsions or suspensions.

In another embodiment, the formulation can be surgically implanted. Suchformulations can include any of the well-known biodegradable andbioerodable carriers, such as polylactides, poly-lactide-co-glycolidesand collagen formulations. Such materials may be in the form of solidimplants, sponges, and the like. In any event, for local use of thematerials, the active ingredients usually are present in the carrier orexcipient in a weight ratio of from about 1:1000 to 1:20,000, but arenot limited to ratios within this range.

The present invention also relates to methods of making pamoate salts ofdonepezil. Specifically, pamoate salts of donepezil can be prepared in avariety of different ways. For example, in one aspect, pamoate salts ofdonepezil can be prepared directly by treating or mixing donepezil (suchas a free base) with pamoic acid in a solvent (such as water, ethanol orDMSO). In another aspect, pamoate salts of donepezil can be prepared bytreating or mixing a donepezil salt (such as a hydrochloride salt) witha pamoate salt (such as disodium pamoate) in one or more solvents. Forexample, donepezil pamoate can be prepared by adding a solution ofdisodium pamoate, or other pamoate salt in an appropriate solvent, suchas water, to a solution of donepezil hydrochloride and leaving thesolution to stir for a period of time, such as, for example, about 3hours, until precipitation occurs. Alternatively, other methods such asevaporation, slurry, anti-solvent, cooling and hydration can also beused to precipitate the salt.

Pamoate salts can also be formed with Rivastigmine (Exelon), Galantamine(Razadyne), Tacrine (Cognex); and Memantine (Namenda), besides Donepezil(Aricept), which are the drugs approved for the treatment of thecognitive symptoms (memory loss, confusion, and problems with thinkingand reasoning) of Alzheimer's disease.

In another aspect, the present invention relates to a solid state formof a rivastigmine salt, wherein the salt is a pamoate salt. The pamoatesalt can be crystalline, anhydrous, hydrated, solvated, or amorphous. Inyet another aspect, the invention relates to crystalline pamoate saltsof rivastigmine having or characterized by one or more of the followingproperties: (1) a powder X-ray diffraction pattern having main peaksexpressed as 2-theta at about 9.8, 19.0, 23.0, 26.8, 36.8 and 37.0±0.2degrees 2-theta; (2) an X-ray power diffraction pattern substantially inaccordance with that shown in FIG. 14; and (3) combinations of (1) and(2). Additionally, the crystalline pamoate salts of rivastigmine canfurther have or be characterized by the powder X-ray diffraction patternshown in Table 7. In still yet another aspect, the present inventionalso relates to compositions containing the above described pamoatesalts of rivastigmine and pharmaceutical compositions containing saidcompositions and at least one pharmaceutically acceptable carrier.

In still another aspect, the present invention relates to a solid stateform of a memantine salt, wherein the salt is a pamoate salt. Thepamoate salt can be crystalline, anhydrous, hydrated, solvated, oramorphous. In yet another aspect, the invention relates to crystallinepamoate salts of memantine having or characterized by one or more of thefollowing properties: (1) a powder X-ray diffraction pattern having mainpeaks expressed as 2-theta at about 7.6, 12.7, 13.2, 18.3, 19.3 and31.8±0.2 degrees 2-theta; (2) an X-ray power diffraction patternsubstantially in accordance with that shown in FIG. 17; and (3)combinations of (1) and (2). Additionally, the crystalline pamoate saltsof memantine can further have or be characterized by the powder X-raydiffraction pattern shown in Table 8. In still yet another aspect, thepresent invention also relates to compositions containing the abovedescribed pamoate salts of memantine and pharmaceutical compositionscontaining said compositions and at least one pharmaceuticallyacceptable carrier.

The following examples are intended to illustrate and not to limit thescope of the present invention.

EXAMPLES Example 1: Making Donepezil Pamoate at a 1:1 Molar Ratio ofDonepezil to Pamoic Acid from DMSO/Water (Mono-Pamoate Salt ofDonepezil)

796 mg of donepezil free base and 776 mg of pamoic acid were dissolvedin 6 ml of DMSO and stirred for 7 hours at room temperature. 30 ml ofwater were added to precipitate the solids. The solids were filtered anddried at 40-60° C. to yield donepezil pamoate at a 1:1 molar ratio ofdonepezil to pamoic acid.

X-ray powder diffraction (“XRPD”) patterns of above solids were obtainedusing a Bruker D8 Advance x-ray powder diffractometer with copper Kαradiation at a wavelength of 1.5406 Å. Instrumental conditions includeda step size of 0.02°/step, a scan rate of 0.2 seconds/step, a 2-thetarange of 3 to 40 degrees, a voltage of 40 kV, a current of 40 mA, and aLynxeye detector. Samples were packed into recessed sample holders foranalysis. A typical example of an x-ray diffraction pattern for anExample 1 salt is shown in FIG. 2. Table 1 sets forth the x-raydiffraction data wherein d(A) represents the interplanar spacing and I %represents the typical relative intensities. The key peaks are boldedand underlined in Table 1.

TABLE 1 2-Theta d (A) I %  5.859 15.0711  33.2  6.322 13.968  12.1 9.601 9.2045 63.1 11.123 7.9479 26.8 11.582 7.6338 22.6 11.809 7.488130.4 12.231 7.2302 11.8 13.109 6.7483 27.5 14.538 6.088  33.1 15.2625.8006 23   16.218 5.4609  7.8 16.843 5.2597  6.1 17.305 5.12  35.417.871 4.9593 14.4 19.191 4.6211 25.7 19.459 4.558  10.3 20.125 4.408734.4 20.698 4.2879 37.7 21.079 4.2112 47.6 21.993 4.0383 16.9 22.3943.9667 100    23.274 3.8188 39.4 23.577 3.7703 17.5 24.455 3.6369 85.625.237 3.526  12.9 25.733 3.4592 26.9 27.277 3.2668 11   27.619 3.227  9.2 28.417 3.1382  6.1 28.879 3.0891  6.5 29.793 2.9963 11.2 30.4052.9375 14.1 30.674 2.9122  7.3 31.108 2.8726 12.7 37.959 2.3684 7 

Example 2: Making Donepezil Pamoate at a 2:1 Molar Ratio of Donepezil toPamoic Acid from DMSO/Water System (Semi-Pamoate Salt of Donepezil)

1554 mg of donepezil free base and 776 mg of pamoic acid were dissolvedin 6 ml of DMSO and stirred for 5 hours at room temperature. 30 ml ofwater were added to precipitate the solids. The solids were filtered anddried at 40-50° C. to yield donepezil pamoate at a 2:1 molar ratio ofdonepezil to pamoic acid. A typical example of an x-ray diffractionpattern for an Example 2 salt is shown in FIG. 3 and the interplanarspacing and typical relative intensities are set forth in Table 2. Thekey peaks are bolded and underlined in Table 2.

TABLE 2 2-Theta d (A) I %  6.13 14.4053 20.8  8.53 10.3574  18.9  9.3719.4302  5.4  9.656 9.1518  6.2 10.341 8.5469  6.5 11.562 7.647  100  12.209 7.2432 57.8 13.298 6.6524 18.3 13.754 6.4329 25.7 15.206 5.822 28.8 15.74 5.6255 21.8 16.269 5.4436 28.8 16.865 5.2527 25.6 17.1325.1714 14.3 17.913 4.9478 18.3 18.201 4.87  9  18.81 4.7138 24.8 19.2094.6168 63.5 19.973 4.4418 36.2 20.334 4.3638 14.9 21.25 4.1777 48.321.728 4.0868 15.2 22.431 3.9604  9.9 23.25 3.8226 49.7 23.52 3.779322   24.169 3.6793 12.8 24.531 3.6259 24.5 27.221 3.2733 18.9 27.6013.2292 36.7

Example 3: Making Donepezil Pamoate at a 1:1 Molar Ratio of Donepezil toPamoic Acid from Donepezil Hydrochloride and Disodium Pamoate in Water.(Semi-Pamoate Salt of Donepezil)

23.2 mg of donepezil hydrochloride were dissolved in 0.8 ml of water.22.5 mg of disodium pamoate were dissolved in 2 ml of water. Thedisodium pamoate solution was added dropwise to the donepezilhydrochloride solution. The resulting mixture was stirred overnight atroom temperature and filtered. The solids were vacuum dried at 50° C. toyield donepezil pamoate at a 1:1 molar ratio of donepezil to pamoicacid.

The XRPD pattern of an Example 3 salt is shown in FIG. 4.

Example 4: Making Donepezil Pamoate at a 2:1 Molar Ratio of Donepezil toPamoic Acid from Donepezil Hydrochloride and Disodium Pamoate in Water(Semi-Pamoate Salt of Donepezil)

2081 mg of donepezil hydrochloride were dissolved in 30 ml of water.1075 mg of disodium pamoate were dissolved in 6 ml of water. Thedisodium pamoate solution was added dropwise to the donepezilhydrochloride solution and 40 ml of water were added to the mixedsolution. The resulting mixture was stirred for 3 hours at roomtemperature and filtered. The solids were vacuum dried at 50° C. toyield donepezil pamoate at a 2:1 molar ratio of donepezil to pamoicacid.

Example 5: Making 1:1 Molar Ratio of Donepezil to Pamoic Acid fromDonepezil Hydrochloride and Disodium Pamoate in Ethanol (Mono-PamoateSalt of Donepezil)

23.02 mg of donepezil hydrochloride salt was dissolved in 0.8 ml ofethanol; 22.98 mg of disodium pamoate was dissolved in 2 ml of ethanol.The two ethanol solutions were combined, stirred overnight, filtered andvacuum dried at 50° C. to yield 1:1 donepezil pamoate.

The XRPD pattern of an Example 5 salt is shown in FIG. 5. It isdifferent from the XRPD patterns shown in FIG. 2 and FIG. 3. Theinterplanar spacing and intensity represents the typical relativeintensities as set forth in Table 3. It was found that the solidsobtained from this process converted to solids with the same XRPDpattern in FIG. 3 following reformation of a slurry in water. The keypeaks are bolded and underlined in Table 3.

TABLE 3 2-Theta d (A) I %  6.625 13.3308  43    7.497 11.7824  32.5 7.993 11.0526  70.7   9.371 9.43   100     9.993 8.844  17.1 11.9817.3807 24.6 12.231 7.2306 25.5 13.338 6.6326 11   13.64 6.4864 26  14.826 5.9703 99.1 15.683 5.646  27.5 16.121 5.4934 68.8 16.767 5.283133.5 17.818 4.9739 79.9 18.274 4.8509 22.5 19.019 4.6623 76.3 19.8954.459  35.5 21.118 4.2035 63.3 21.994 4.0379 85.9 22.261 3.9902 71.623.061 3.8535 74.4 23.994 3.7057  5.9 24.261 3.6656  9.2 24.664 3.606623.1 25.083 3.5473 16.3 26.497 3.3611 10.9 27.048 3.2939 23.5 27.4473.2469 20.2 29.296 3.046  24   29.987 2.9774  6.8 30.769 2.9035  9.731.759 2.8152 12.5 32.537 2.7497  5.3 33.855 2.6455  7.9 35.721 2.5115 5.6 36.587 2.454   4.8 37.309 2.4082  6.3 37.996 2.3662  5.7 39.0242.3062  8.8

Example 6: Characterization of Donepezil Pamoates by DifferentialScanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and NuclearMagnetic Resonance Spectroscopy (NMR)

Donepezil pamoates (1:1 and 2:1) were analyzed using DSC, TGA and NMR.The DSC and TGA thermograms are shown in FIG. 6 and FIG. 7,respectively, indicating the existence of hydrates or solvates andpresence of different crystal forms (polymorphic Form A and Form B).

The NMR spectra are provided in FIGS. 8-10. FIG. 8 is the NMR spectrumof the 1:1 salt prepared in DMSO/water (XRPD Pattern with d spacing asshown in Table 1). The molar ratio of donepezil to pamoate wasapproximately 1:1 measured from proton integration of the ¹H NMRspectrum. ¹H NMR (400 MHz, DMSO-d6) chemical shifts were recorded at(all values in ppm) 8.34 (s, 2H), 8.18 (d, 2H), 7.76 (d, 2H), 7.53 (m,2H), 7.47 (m, 3H), 7.25 (t, 2H), 7.11 (t, 3H), 7.04 (s, 2H), 4.76 (s,2H), 4.31 (s, 2H), 3.84 (s, 3H), 3.79 (s, 3H), 3.18 (m, 1H), 2.92 (m,2H), 2.62 (m, 2H), 1.97-1.30 (m, 9H). FIG. 9 is the NMR spectrum of the2:1 salt prepared in DMSO/water (XRPD Pattern with d spacing as shown inTable 2). The molar ratio of donepezil to pamoate was approximately 2:1measured from proton integration of the ¹H NMR spectrum. ¹H NMR (400MHz, DMSO-d6) chemical shifts were recorded at (in ppm) 8.21 (m, 4H),7.67 (d, 2H), 7.75-7.44 (m, 10H), 7.15 (t, 2H), 7.02 (m, 6H), 4.71 (s,2H), 4.21 (s, 4H), 3.85 (s, 6H), 3.78 (s, 6H), 3.21 (m, 2H), 2.81 (m,4H), 2.61 (m, 4H), 1.94-1.30 (m, 18H). FIG. 10 is the NMR spectrum ofthe 1:1 salt prepared in ethanol (XRPD Pattern with d spacing as shownin Table 3). The molar ratio of donepezil to pamoate was approximately1:1 measured from proton integration of the ¹H NMR spectrum. ¹H NMR (400MHz, DMSO-d6) chemical shifts were recorded at (in ppm) 8.21 (m, 4H),7.65 (d, 2H), 7.44 (m, 2H), 7.43 (m, 3H), 7.14 (t, 2H), 7.03 (m, 4H),4.70 (s, 2H), 4.19 (s, 2H), 3.84 (s, 3H), 3.78 (s, 3H), 3.21 (m, 1H),2.78 (m, 2H), 2.62 (m, 2H), 1.93-1.27 (m, 9H).

Example 7: A Comparison of In Vivo Absorption of Donepezil Pamoate inRats Following a Single Intramuscular Dose with Donepezil Pamoate (2:1)

Physicochemical characterization studies have showed that donepezilpamoate (2:1) is the most stable form of donepezil pamoate salt.Therefore, a pharmacokinetic study was performed in rat model toevaluate in vivo absorption characteristics of the donepezil pamoate(2:1) following a single dose intramuscular administration usingdonepezil hydrochloride solution as a reference. Ten (10) female ratsthat weighed 300±30 grams were randomly divided into 2 groups of 5 ratseach. Donepezil pamoate (2:1) suspension and donepezil hydrochloridesolution were administered to each group, respectively, throughintramuscular (IM) injection into the rear legs at a dose of 13.5 mg/kg(in donepezil). In the pharmacokinetic study, donepezil hydrochloridesolution were prepared using saline solution, donepezil pamoate (2:1) issuspended using the diluent which is composed of carboxymethylcellulosesodium, mannitol, polysorbate 80, sodium hydroxide and/or hydrochloricacid for pH adjustment, and water for injection. Blood samples werecollected and transferred into tubes containing anticoangulant, heparin.The plasma samples are separated into labeled tubes and stored frozen at−20° C. until they were analyzed using a HPLC-MS method. 500 μL of bloodwas drawn for each time point. The time intervals selected to obtainplasma samples were 15 minutes, 30 minutes, 45 minutes, 60 minutes, 90minutes, 2 hours, 4 hours, 6 hours, 8 hours, 12 hours, 24 hours and 48hours, for the donepezil hydrochloride solution injection and 30minutes, 90 minutes, 2 hours, 4 hours, 8 hours, 24 hours, 48 hours, 56hours, 72 hours, 144 hours, 192 hours, 288 hours and 336 hours for theDonepezil pamoate (2:1) suspension injection, respectively.

The results are shown in FIG. 11. Specifically, FIG. 11 demonstratesthat donepezil hydrochloride salt solution is rapidly absorbed and theneliminated after a single intramuscular injection. In contrast, after asingle intramuscular injection of the donepezile pamoate (2.1), asustained level of donepezil plasma concentrations was maintainedfollowing an initial faster absorption within the first hour therebydemonstrating that extended release of donepezil was achieved usingdonepezil pamoate.

Example 8: Summary of Donepezil Pamoate Salt Screen with DifferentSolvent Systems

This example provides a summary of the donepezil pamoate salt screensdescribed in the above examples. The inventors found that the solvent toprepare the salt was important as many salts did not work for saltformation.

When ethanol (the amount of ethanol that can be used is enough todissolve the donepezil free base; in fact, the ratio of free base toethanol can be as high as 5:1 free base to ethanol) and pamoic acid (theacid to ethanol ratio can be as high as 10:1 pamoic acid to ethanol),are used as solvent system for salt formation, a mono-pamoate salt ofdonepezil is obtained exclusively regardless of the ratio of the freebase of donepezil and pamoic acid used.

When DMSO and water is used as solvent system for salt formation, amono-pamoate salt is obtained if a 1:1 ratio of the free base ofdonepezil and pamoic acid is used and a semi-pamoate salt of the productis obtained if a 2:1 ratio of the free base of donepezil and pamoic acidis used.

When water (the ratio of free base to water that can be used is 70:1 andthe ratio of the acid to water is about 180:1) is used as solvent systemfor salt formation, a semi-pamoate salt of donepezil is the only productobtained when a 1:1 or 2:1 ratio of the free base of donepezil andpamoic acid is used.

Table 4 below describes the various solvents that can be used to obtainpamoate salts of donepezil.

TABLE 4 Ratio of free base of donepezil Solvent to pamoic acid Saltobtained Ethanol 1:1 and 2:1 Mono-pamoate is obtained only DMSO andwater 1:1 Mono-pamoate of donepezil DMSO and water 2:1 Semi-pamoate ofdonepezil Water alone 1:1 or 2:1 Semi-pamoate salt of donepezil isobtained only

All pamoate salts obtained using the above solvent systems contain about4-9% (by weight) of water content based on loss on dry studies. Thedonepezil pamoate salt (hydrated, 2:1 ratio) is the most stable salt.When this hydrated salt is heated at an elevated temperature (such as upto 120° C.) it will convert to the anhydrous form which is not stable.At this point, the anhydrous form will absorb moisture from theatmosphere and gradually convert back to the hydrate form.

Example 9: Polymorph Studies

2080 mg of donepezil HCl is weighed and dissolved in 30 mL of waterwhile stirring to provide Solution A. 1075 mg of pamoate disodium isweighed and dissolved in 6 mL of water while stirring to provideSolution B. Solution A is added into Solution B to which 40 mL of waterwas added. The resulting solution was stirred for at least 3 hoursbefore being filtered. The solid material obtained from filtration isdried under vacuum to yield Donepezil pamoate salt. The X-ray powderdiffraction, thermogravimetric analysis/differential scanningcalorimetry and H-studies of this salt identified this salt as “HydratedForm”. The hydrated salt can be converted into another polymorphic form(designated as “Anhydrous Form”) when dried at 120° C. The X-ray powderdiffraction data for Hydrated (Also referred to as “Form A” herein) andAnhydrous Forms (Also referred to as “Form B” herein) are shown in FIGS.12 and 13. The Hydrated Form is characterized with X-ray powderdiffraction as shown in FIG. 12. The X-ray powder diffraction data isalso shown below in Table 5. The key peaks are bolded and underlined inTable 5.

TABLE 5 2-Theta d Height I % Area I %  6.183 14.2818  605 16.9  929415.6  8.606 10.266  682 19.1  8941 15    9.446 9.3545 197  5.5  3498 5.9  9.706 9.1052 223  6.2  3479  5.8 10.425 8.4786 207  5.8  2887  4.911.592 7.6278 3574   100    50863 85.5 12.271 7.2072 2337   65.4 3499058.8 13.354 6.625  797 22.3 15340 25.8 13.812 6.4059 1112  31.1 1958732.9 15.274 5.7961 1110  31.1 12662 21.3 15.814 5.5992 810 22.7 1166719.6 16.296 5.4348 1198  33.5 15006 25.2 16.936 5.2308 971 27.2 1961833   17.216 5.1464 578 16.2 12703 21.3 17.978 4.9301 694 19.4  9583 16.118.84 4.7063 1053   29.5 34003 57.1 19.259 4.6049 2644   74    4367473.4 20.041 4.4269 1512  42.3 30683 51.6 21.301 4.1677 2375  66.5 4429774.4 21.802 4.0732 647 18.1 13745 23.1 22.503 3.9478 504 14.1  8412 14.123.304 3.8138 2350   65.8 43783 73.6 23.583 3.7694 1098  30.7 34544 58  24.246 3.6678 612 17.1 16323 27.4 24.644 3.6094 1403   39.3 34239 57.525.308 3.5162 292  8.2  5300  8.9 26.426 3.3699 261  7.3  2243  3.827.31 3.2628 1058   29.6 50410 84.7 27.67 3.2213 2016  56.4 59519 100  29.152 3.0607 193  5.4  5352 9  29.772 2.9984 173  4.8  3892  6.5 30.6752.9122 176  4.9  3910  6.6 31.133 2.8704 237  6.6  4714  7.9 31.9552.7984 204  5.7  5324  8.9 32.378 2.7628 133  3.7  4691  7.9 32.9492.7162  84  2.4  566 1  33.458 2.676 216 6   3508  5.9 34.601 2.5902 171 4.8  3235  5.4 36.138 2.4835 296  8.3  6286 10.6 37.426 2.4009 101  2.8 860  1.4 38.329 2.3464  98  2.7  1792 3 

The Anhydrous Form is characterized with X-ray powder diffraction asshown in FIG. 13. The X-ray powder diffraction data is also shown belowin Table 6. The key peaks are bolded and underlined in Table 6.

TABLE 6 2-Theta d Height I % Area I %   6.309 13.9981   398 35.3 470225.4  8.484 10.4131  264 23.4 3600 19.5  9.23 9.5737 246 21.8 2083 11.3 9.851 8.9711 138 12.3 2478 13.4 10.386 8.51  215 19.1 3508 19   11.9127.4232 1126   100    18504   100    12.724 6.9512 112  9.9  891  4.813.97 6.3342 328 29.1 5955 32.2 14.211 6.227  209 18.6 6470 35   14.8335.9675 201 17.9 1980 10.7 15.452 5.7297 175 15.5 1302 7  16.157 5.4814356 31.6 5170 27.9 16.811 5.2695 138 12.3  621  3.4 17.196 5.1523 16915   3960 21.4 17.638 5.0242 158 14   3390 18.3 18.225 4.8637  88  7.81884 10.2 18.479 4.7975  96  8.5 1878 10.1 19.716 4.499  373 33.1 413022.3 20.362 4.3577 364 32.3 6536 35.3 21.082 4.2107 403 35.8 5197 28.122.226 3.9964 123 10.9 2750 14.9 22.583 3.9339 126 11.2 2755 14.9 23.7043.7504 431 38.3 7905 42.7 24.185 3.677  211 18.7 5368 29   24.907 3.572 157 13.9 1194  6.5 25.93 3.4333  86  7.6 1507  8.1 27.99 3.1851 125 11.13291 17.8 28.593 3.1194 108  9.6  756  4.1

Example 10: Preparation of Rivastigmine Pamoate Salt

A solution of 20 mg of rivastigmine tartrate in 0.25 mL ethanol wasadded to a solution of 20 mg of pamoate disodium salt in 0.25 mLethanol. The resulting solution was stirred for 4 hours and thencentrifuged. The wet product was dried at 60° C. under vacuum to yield aRivastigamine pamoate salt (1:1 ratio). The salt is characterized withX-ray powder diffraction, differential scanning calorimetry and NMR asshown in FIGS. 14-16. The X-ray powder diffraction data is also shownbelow in Table 7. The key peaks are bolded and underlined in Table 7.

TABLE 7 2-Theta d Height I % Area I %  4.756 18.5639  239 7.8 2036  9.1  9.847 8.9754 3046   100     22438   100    11.965 7.3906 220 7.2 1489 6.6 14.334 6.1738 302 9.9 2384 10.6 15.546 5.6952 873 28.7  6489 28.918.946 4.6803 828 27.2   7948 35.4 19.707 4.5011 821 27   7558 33.720.773 4.2724 637 20.9  5831 26   22.221 3.9972 103 3.4 1046  4.7 22.9473.8724 2461   80.8   21213   94.5 23.939 3.7142 118 3.9 1898  8.5 24.1683.6795  82 2.7 2194  9.8 24.55 3.6231 705 23.1  6215 27.7 25.563 3.4818428 14.1  6626 29.5 25.907 3.4363 383 12.6  4060 18.1 26.396 3.3738  812.7  658  2.9 26.725 3.3329 536 17.6  4835 21.5 28.841 3.093  283 9.33277 14.6 29.697 3.0058  77 2.5  958  4.3 29.91 2.9849 177 5.8 2675 11.930.179 2.9589 345 11.3  3663 16.3 31.28 2.8572 697 22.9  5959 26.632.007 2.7939 840 27.6  7422 33.1 33.384 2.6818 132 4.3 1242  5.5 33.6072.6645 186 6.1 3699 16.5 34.143 2.6239 285 9.4 4799 21.4 34.849 2.5723115 3.8  963  4.3 35.426 2.5317  75 2.5  716  3.2 36.278 2.4742 50316.5  6085 27.1 36.847 2.4373 349 11.5   8055 35.9 37.042 2.4249 69922.9   8699 38.8 37.442 2.3999  70 2.3  292  1.3 38.396 2.3425  90 3   870  3.9 38.889 2.3139 427 14   6105 27.2 39.279 2.2918 155 5.1 1435 6.4 39.901 2.2575  23 0.8 −230 −1  

Example 11: Preparation of Memantine Pamoate Salt

A solution of 22 mg of memantine hydrochloride in 0.25 mL ethanol wasadded to a solution of 39 mg of pamoate disodium salt in 0.25 mLethanol. The resulting solution was stirred at room temperature for 4hours and then centrifuged. The wet product obtained was dried at 60° C.under the vacuum to yield memantine pamoate salt (1:1 ratio). The saltis characterized with X-ray powder diffraction, differential scanningcalorimetry and NMR as shown in FIGS. 17-19. The X-ray powderdiffraction data is also shown below in Table 8. The key peaks arebolded and underlined in Table 8.

TABLE 8 2-Theta d Height I % Area I %  5.217 16.9248  117 2.3 1668 4.2  7.559 11.6862   4673   93.3   37155   92.6    8.381 10.5414  370 7.42170 5.4 11.066 7.9886 1360  27.2  9847 24.5  11.836 7.4705 310 6.2 20135   12.743 6.941   4358   87.1   36773   91.6   13.243 6.6801 4129  82.5   32226   80.3   14.043 6.3013 728 14.5  4119 10.3  15.222 5.8156689 13.8  5442 13.6  16.232 5.4562 417 8.3 3323 8.3 16.768 5.2828 2267 45.3  19323  48.1  18.37 4.8256 5006   100     40141   100     19.3064.5937 2896   57.9   23722   59.1   19.627 4.5194 720 14.4  5871 14.6 20.135 4.4064 161 3.2 1233 3.1 20.506 4.3275 708 14.1  5723 14.3  20.9734.2321  81 1.6  195 0.5 21.388 4.1511 357 7.1 2768 6.9 22.151 4.0098 51810.3  4298 10.7  22.681 3.9172 1087  21.7  9862 24.6  22.966 3.8693 70114   6183 15.4  23.427 3.7942  57 1.1 −227 −0.6  24.138 3.684  249 5  1989 5   24.952 3.5656 279 5.6 2774 6.9 25.595 3.4774 190 3.8 1716 4.325.884 3.4393  61 1.2  600 1.5 26.305 3.3852 107 2.1 1193 3   26.5883.3497 523 10.4  6016 15   26.99 3.3008 461 9.2 5102 12.7  27.45 3.2466245 4.9 2441 6.1 28.219 3.1598 100 2   1313 3.3 28.834 3.0938  53 1.1 194 0.5 29.473 3.0281 108 2.2 1179 2.9 29.828 2.993  118 2.4  936 2.330.142 2.9624 140 2.8 2145 5.3 30.367 2.941   82 1.6 1452 3.6 30.9762.8846 204 4.1 1994 5   31.797 2.8119 2387   47.7   26003   64.8  33.553 2.6686 162 3.2 1657 4.1 35.213 2.5466  98 2   1279 3.2 35.6482.5165  89 1.8 1048 2.6 37.691 2.3846 129 2.6 1962 4.9 39.205 2.2959  631.3  513 1.3 39.683 2.2694  71 1.4  508 1.3

What is claimed is:
 1. A compound, which is a polymorphic form ofpamoate salt of memantine, characterized by a powder X-ray diffractionpattern having peaks expressed as 2-theta at about 7.6, 12.7, 13.2,18.3, 19.3, and 31.8±0.2 degrees 2-theta.
 2. A pharmaceuticalcomposition comprising a compound of claim 1 and a pharmaceuticallyacceptable carrier.
 3. A method of treating dementia associated withAlzheimer's disease, the method comprising administering to a subject inneed thereof a therapeutically effective amount of a pharmaceuticalcomposition comprising a compound of claim 1 and at least onepharmaceutically acceptable carrier.
 4. The method of claim 3, whereinthe composition is administered by injection.
 5. The method of claim 3,wherein the composition is administered intramuscularly orsubcutaneously.